Premiership Rugby's rugby director Phil Winstanley is "very confident" that there are no clubs currently spending over the salary cap in the Aviva Premiership.

With the transfer market now in full flight following Saracens' swoops for Wasps' Billy Vunipola and Harlequins' James Johnston, the Guardian claims that some coaches have said that a few of the teams in England's top flight are cheating the system and spending over the nominated salary cap of £4.5m.

London Irish's Brian Smith, who is preparing for life without star England duo Alex Corbisiero and Jonathan Joseph who both look set to leave the club, said previously on the subject of the transfer market: "I've no doubt a number of our lads have been worked on since very early in the season. Some clubs are paying £2m on their coaching staff. Some teams are cheating the salary cap and spending twice what we do on our squad."

But Winstanley claims that while he has heard "rumours" of clubs over-spending, he is adamant that the teams are adhering to the £4.5m limit. "We are very much aware of what's going on within each club," Winstanley told the Guardian. "Until we can prove otherwise then as far as I'm concerned there is no breach of the salary cap.

"Are we aware of the rumours? Of course we are. I'm not naive. It's not falling on deaf ears. But we have a robust system with extensive powers. I'm not going to talk about individual clubs but every club is subject to them. This is a regular topic at our board meetings … every club is completely aware of the process and the potential sanctions."